In a semiconductor device manufacturing process, a plasma of a processing gas is often used and, thus, parameters related to plasma generation are important. The parameters related to the plasma generation include, e.g., a degree of depressurization in a processing chamber, a frequency of a high frequency power, and a flow rate of a processing gas. The flow rate of the processing gas is controlled by a gas flow rate controller such as a FCS (Flow Control System) (Registered Trademark), a MFC (Mass Flow Controller) or the like. However, a set value of a flow rate in the gas flow rate controller may not be equal to an actually controlled flow rate due to a manufacturing error, temporal deterioration or the like. Accordingly, the gas flow rate controller is calibrated upon shipping or regular maintenance.
As for a method for calibrating a gas flow rate controller, there is known a method of comparing a set flow rate and an actual flow rate calculated from a gas pressure and a gas temperature of a build-up tank, which has a known inner volume and is connected in series to a gas flow rate controller, by allowing a set flow rate of gas to flow into the buildup tank (see, e.g., Japanese Patent Application Publication No. 2012-32983). In addition, there is also known a method of, by measuring gas temperatures and gas pressures at different timings in case of allowing a gas to flow into a line which is provided at a downstream side of a gas flow rate controller and has a known inner volume and obtaining masses of gases introduced at the respective timings from the measured gas temperatures and gas pressures, checking an absolute flow rate of the gas flow rate controller from a difference between the masses of gases (see, e.g., Japanese Patent Application Publication No. 2006-337346).
Further, as for a method for calculating a volume of a processing chamber, there is known a method of estimating a volume of a processing chamber based on variation of gas pressures in a line and in the processing chamber by introducing a gas at a predetermined flow rate into the line having a known inner volume and then into the processing chamber:
In the method described above such as the method of calibrating a gas flow rate controller or the method of calculating a volume of a processing chamber, it is considered that a gas temperature is equal to a room temperature or a temperature in a line.
However, an actual gas temperature in the line or in the build-up tank may be different from the room temperature or the temperature in the line. In that case, the calibration of the gas flow rate controller or the calculation of the volume of the processing chamber may not be performed with accuracy. Further, the line is often accommodated in a gas box or the like and, thus, it is difficult to additionally provide a temperature sensor. Accordingly, it is difficult to directly measure a gas temperature in the line.